<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style type="text/css">
* {
  margin: 0;
  padding: 0;
}
body {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: #0e92b3;
}
.form {
  width: 300px;
  background-color: rgb(41, 45, 62);
  color: #fff;
  border-radius: 2px;
  padding: 50px 80px 80px;
  border-radius: 10px;
  box-shadow: 2px 2px 2px rgba(0, 0, 0, 0.4);
}
.header {
  text-align: center;
  font-size: 35px;
  text-transform: uppercase;
  line-height: 100px;
}

.main .inpbox input {
  background-color: rgb(41, 45, 62);
  border: 0;
  width: 100%;
  text-align: center;
  font-size: 15px;
  color: #fff;
  outline: none;
}

.main .inpbox {
  background: linear-gradient(90deg, #03a9f4, #f441a5, #ffeb3b, #03a9f4);
  background-size: 400%;
  width: 100%;
  height: 50px;
  margin-bottom: 20px;
  border-radius: 30px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 1s;
}
.main .inpbox input {
  height: calc(100% - 4px);
  width: calc(100% - 6px);
  border-radius: 30px;
}

.main .inpbox:has(input:focus) {
  animation: animate 5s linear infinite;
  transform: scale(1.2);
}
@keyframes animate {
  0% {
    background-position: 0 0;
  }
  100% {
    background-position: 400% 0;
  }
}
.action {
  display: flex;
  justify-content: center;
}
.action .btn {
  width: 60%;
  text-transform: uppercase;
  border: 2px solid #0e92b3;
  text-align: center;
  line-height: 50px;
  border-radius: 30px;
  cursor: pointer;
  transition: all 1s;
}
.action .btn:hover {
  transform: scale(1.2);
  background-color: #0e92b3;
}
</style>
</head>
<body>
  <div class="form">
    <div class="header">login</div>
    <div class="main">
      <div class="inpbox">
        <input type="text" placeholder="username">
      </div>
      <div class="inpbox">
        <input type="password" placeholder="password">
      </div>
    </div>
    <div class="action">
      <div class="btn">login</div>
    </div>
  </div>
</body>
</html>